The present invention relates to an implantable drug delivery device for infusing a therapeutic agent into an organism, and more particularly, relates to an improved peristaltic implantable pump with improved occlusion along a drug delivery pump tube.
Implantable drug infusion devices are well known in the art. These devices typically include a medication reservoir within a generally cylindrical housing. Some form of fluid flow control is also provided to control or regulate the flow of fluid medication from the reservoir to the outlet of the device for delivery of the medication to the desired location in a body, usually through a catheter. These devices are used to provide patients with a prolonged dosage or infusion of a drug or other therapeutic agent.
Active drug infusion devices feature a pump or a metering system to deliver the drug into the patients system. An example of such a drug infusion pump currently available is the Medtronic SynchroMed programmable pump. Additionally, U.S. Pat. Nos. 4,692,147 (Duggan), 5,840,069 (Robinson), and 6,036,459 (Robinson), assigned to Medtronic, Inc., Minneapolis, Minn., disclose body-implantable electronic drug administration devices comprising a peristaltic (roller) pump for metering a measured amount of drug in response to an electronic pulse generated by control circuitry associated within the device. Each of these patents is incorporated herein by reference in their entirety for all purposes. Such devices typically include a drug reservoir, a fill port, a peristaltic pump having a motor and a pumphead to pump out the drug from the reservoir, and a catheter port to transport the drug from the reservoir via the pump to a patient""s anatomy. The drug reservoir, fill port, peristaltic pump, and catheter port are generally held in a housing, or bulkhead. The bulkhead typically has a series of passages extending from the drug reservoir and through the peristaltic pump that lead to the catheter port, which is typically located on the side of the housing. The peristaltic pump comprises a pumphead having rollers, a race or cavity defined by the bulkhead, and a pump tube that is threaded or inserted between the rollers and the race. The peristaltic pumps use the rollers to move a drug through the pump tube from the drug reservoir to the catheter port. The drug is then pushed by the pump through a catheter connected to the catheter port, and is delivered to a targeted patient site from a distal end of the catheter.
The prior art delivery devices, however, are limiting in that the load that the rollers place on the tube can vary as the rollers move along the tube. If the load is excessive, excess energy will be consumed and the tube life will be shortened, resulting in increased replacement costs. If the load is insufficient, inadequate occlusion of the tube will result in leakage of fluid past the roller, reducing the accuracy of the pump. Variation in the load is caused by variations in the gap between the rollers and the race in which the pump tube lies, the gap variance being due to manufacturing tolerances associated with the tube, the race and the pumphead. Prior art solutions to the load variance problem include tight manufacturing tolerances, sorting and matching of components, and placing shims of appropriate thickness between the rollers and the tube, each of which increases manufacturing costs and reduces manufacturing flexibility.
It is an object of the present invention to provide an implantable drug infusion device which reduces or wholly overcomes some or all of the difficulties inherent in prior known devices. Particular objects and advantages of the invention will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure of the invention and detailed description of preferred embodiments.
The present invention provides an implantable drug infusion device which features a peristaltic pump having a new configuration, in which a spring biases a roller assembly against a pump tube, thereby minimizing the variation in the load that the roller assembly places on the pump tube.
In accordance with a first aspect, an implantable drug infusion device comprises a peristaltic pump, including a pump tube for holding a liquid to be pumped. A race is configured to support the tube along a path. A roller assembly is configured to compress the tube against the race at one or more points along the path, and the roller assembly includes at least one roller. A drive assembly drives the roller assembly relative to the tube along the path so as to move the liquid through the tube. A biasing member is operably connected to the one roller to adjustably bias the roller against the tube.
In accordance with another aspect, an implantable drug infusion device includes a bulkhead having a race. A pump tube having an inlet and an outlet is positioned within the race, the race configured to support the tube along a path. A roller assembly is configured to compress the tube against the race at least one point along the path, and the roller assembly includes a hub and at least one roller biased against the pump tube. A drive assembly drives the roller assembly relative to the tube along the path so as to move a liquid through the tube. A biasing member is operably connected to the roller to adjustably bias the at least one roller against the tube.
In accordance with yet another aspect, an implantable drug infusion device includes a bulkhead having a race, a first chamber, and a second chamber. A pump tube has an inlet and an outlet and is positioned within the race, the race configured to support the tube along a path. A motor assembly is positioned within the first chamber, a pumphead assembly is positioned within the second chamber, and the motor assembly drives the pumphead assembly. A drive assembly drives the roller assembly relative to the tube along the path so the rollers compress the tube to move a liquid through the tube. A spring is operably connected to each roller assembly to bias a corresponding roller against the tube.
In accordance with another aspect, the pumphead assembly includes a roller assembly comprising at least two biasing members or springs operably connected to each roller to adjustably bias the roller against the pump tube, wherein the biasing members form an angle. This roller assembly provides biasing or spring loading to the rollers that provide occlusion to the pump tube and thus move a drug through the pump tube. In a preferred embodiment, the roller assembly comprises three rollers contained within three corresponding roller housings, each roller housing operably connected to the other two roller housings by a biasing member or spring. Thus, at each roller housing is a pair of operably connected biasing members or springs, which form an angle. This triangular arrangement of springs provides a compact design with a low spring rate at each roller. The low spring rate at each roller provides for low variations in occlusion load and for changes in roller distance from the pump shaft. This triangular spring arrangement can be characterized as a xe2x80x9clivexe2x80x9d bobbin roller assembly, wherein each roller housing is operably connected to an adjacent roller housing by a biasing member or spring. Further, components or parts for this bobbin roller assembly can be readily made using injection molding processing. More specifically, the parts that can be readily made using injection molding processing include an upper plate, a lower plate, and the three roller housings.
From the foregoing disclosure, it will be readily apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this area of technology, that the present invention provides a significant advance over the prior art. Preferred embodiments of the implantable infusion device of the present invention can significantly reduce the variation in load placed by the roller assembly on the pump tube. This will allow for less stringent manufacturing tolerances, increased manufacturing flexibility, increased tube life, and improved performance. These and additional features and advantages of the invention disclosed here will be further understood from the following detailed disclosure of preferred embodiments.